Subsidiary supply for hydraulic brake booster

ABSTRACT

A vehicle brake applying mechanism which utilizes a dual source of fluid under pressure to assist the vehicle operator in slowing or stopping the vehicle. The mechanism includes a hydraulic brake booster comprising an operator controlled piston slidably located in a housing for movement at the will of the operator, through the manipulation of valve means to thereby establish a braking force in a master cylinder to which the piston is connected. Under normal conditions the brake booster receives its main source of fluid under pressure from an engine-driven pump which also supplies fluid to the vehicle&#39;&#39;s steering gear. However, an independent subsidiary source of fluid under pressure is supplied to the booster should the main source of fluid reach a predetermined minimum value. The subsidiary source is activated or rendered effective by a low flow sensitive switch located in the main supply for energizing an electric pump which is in communication with the booster piston via the valve means. The subsidiary source also actuates a shut-off valve interposed between the booster and steering gear to disestablish flow to the gear, thus conserving the subsidiary source for booster use only.

United States Patent Fulmer [54] SUBSIDIARY SUPPLY FOR HYDRAULIC BRAKEBOOSTER 72] Inventor: Keith H. Fulmer, South Bend, Ind.

[73] Assignee: The Bendix Corporation [22] Filed: Feb. 4, 1971 [21]Appl.N0.1 112,524

Primary Examiner-Edgar W. Geoghegan Attorney-l en C. Decker and Plante,Hartz, Smith and Thompson [45] July 18,1972

57 ABSTRACT A vehicle brake applying mechanism which utilizes a dualsource of fluid under pressure to assist the vehicle operator in slowingor stopping the vehicle. The mechanism includes a hydraulic brakebooster comprising an operator controlled piston slidably located in ahousing for movement at the will of the operator, through themanipulation of valve means to thereby establish a braking force in amaster cylinder to which the piston is connected. Under normalconditions the brake booster receives its main source of fluid underpressure from an engine-driven pump which also supplies fluid to thevehicle's steering gear. However, an independent subsidiary source offluid under pressure is supplied to the booster should the main sourceof fluid reach a predetermined minimum value. The subsidiary source isactivated or rendered effective by a low flow sensitive switch locatedin the main supply for energizing an electric pump which is incommunication with the booster piston via the valve means. Thesubsidiary source also actuates a shut-off valve interposed between thebooster and steering gear to disestablish flow to the gear, thusconserving the subsidiary source for booster use only.

10 Claims, 2 Drawing Figures ELECTRIC PUMP PATENTED JUL 1 8 I9?!INVENTOR KEITH H. FULMER ATTORNEY SUBSIDIARY SUPPLY FOR HYDRAULIC BRAKEBOOSTER BACKGROUND OF THE INVENTION The invention concerns a vehiclefluid pressure system having a fluid operated brake booster therein forconverting a manual input force into an amplified output force, and morespecifically a booster which is provided with a subsidiary source offluid pressure for actuating the master cylinder of a hydraulic brakingsystem at times when the main fluid pressure source communicating withsaid booster is inadequate to achieve vehicle braking.

A booster of the aforementioned type employing two such sources of fluidpressure but utilizing different valve construction for controlling therespective fluid pressure sources is shown in US. Pat. Application Ser.No. 73,933, filed Sept. 21, 1970, owned by the assignee of the presentinvention. The present invention relates to improvements in theutilization of two fluid pressure sources used in connection with afluid operated brake booster, thereby minimizing the danger due to theloss of brakes in the event the main fluid pressure source fails.

SUMMARY OF THE INVENTION In view of the foregoing, an important objectof my invention is to provide in a vehicle hydraulic system, a hydraulicboost mechanism having a subsidiary source of fluid available in theevent the main source of fluid reaches a predetermined minimum flow assensed in the main source return line.

Another important object of my invention is to provide in a vehiclehydraulic system, including a hydraulic boost mechanism and a steeringgear, a subsidiary source of fluid for operating said boost mechanismonly, should the main source of fluid which supplies the vehiclehydraulic system diminish to some predetermined minimum value.

The above and other objects and features of the present invention willbecome apparent from the following description taken in connection withaccompanying drawing.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a view, partially in section, of ahydraulic boost mechanism constructed in accordance with the inventionwhich is disclosed in association with other elements of the vehiclehydraulic system illustrated schematically; and

FIG. 2 is a cross-sectional view of the boost mechanism taken along theline 2-2 of FIG. I.

DETAIL DESCRIPTION Referring now to FIG. I, the reference numeraldesignates a hydraulic boost mechanism located ina vehicle hydraulicsystem comprising an engine driven pump 12 and a steering gear 14operatively connected to the vehicle wheels in a manner well known tothose skilled in the art. The boost mechanism 10, which may be termedmore specifically a hydraulic brake booster, includes a housing 16provided with a bore 18. The brake booster housing 16 is equipped withan inlet port 20 which is in fluid communication with a main hydraulicsource of fluid from the pump 12 through conduit 22. A conduit 24connects working port 26 in the housing 16 to the device 14, which inthis particular system is a steering gear. A return line 28 carries thereturn fluid from the gear 14 to the pump 12 for recirculation.

Piston means 30 is reciprocally located in the bore 18 of the housing16, dividing said bore into two chambers 32 and 34 at the respectiveends of said piston means. The piston means includes a piston 35 and asleeve 36, the latter of which is formed with circumferential grooves orrecesses 38 and 40 which maintain registry with the working port 26 andinlet port 20, respectively, during movement of the piston means in saidbore. The piston is also formed with a circumferential groove or recess42 communicating with groove 38 at all times through passage 44 in thesleeve 36. A pin46, located in the sleeve, projects into the groove 42for engagement with the land 47 to restrict the longitudinal separationbetween the sleeve and piston. Telescoping of the piston 35 within thesleeve 36 is controlled by engagement between land 48 of the piston andend 50 of the sleeve. It is noted that groove 42 maintains communicationwith passage 44 during the telescoping action between the piston and thesleeve. The piston 35 is further formed with a circumferential groove 52between the lands 48 and 51, the latter of which is provided with a seal54 which prevents leakage between the grooves 42 and 52. As is commonlyknown to those skilled in the art, the other lands formed on the sleeveand piston are likewise equipped with the necessary seals. Locatedwithin a central cavity or recess 56 of the piston 35 is valve means 58for controlling reciprocation of said piston 35 in actuating a brakemaster cylinder, not shown, through a force transmitting rod 60, in amanner well known to those skilled in the art. A spring 62 is interposedbetween an end closure 64 and one end of the piston 35 to normally urgethe piston to the right end of the bore, as viewed in the drawing.

The valve means 58 is of the so-called open-center type which allows thepump 12 to freely circulate fluid through the brake booster 10 to thesteering gear in the absence of vehicle braking. In this position fluidflows from the inlet port 20 to the working port 26 by way of recesses40 and 52, radial passage 53, between seat 72 and the valve element 68,passage 55, recess 42, passage 44 and recess 38. The valve meanscomprises a tubular valve member 66 on one end of which is carried avalve element 68 for engagement with valve seats 70 and 72 respectively,depending on whether the brake booster is unapplied (as shown) orapplied. In the latter case, the valve member is unseated from seat 70and seated on seat 72. Valve seat 72 is formed on a ring element 69having axial passage 71 to maintain fluid flow to said steering gear 14during brake boost actuation when the valve element 68 bears against theseat 72. These passages 71 act as a by-pass for valve member 66 whenseated on seat 72 to insure an adequate supply of fluid to the device14. In the brake booster applying position, the operator pushes onthrust member 74 urging it together with valve member 75 into seatingrelationship with valve element 68. Further movement of the thrustmember unseats the element 68 to communicate the chamber 34 with theinlet 20. Fluid from the inlet port enters the passage 53 and passesbetween the seat 70 and valve element 68 of valve member 66, intochamber 34 where the fluid acts on the right end of the piston 35 urgingit leftward, as viewed in the drawing. Upon removal of the force appliedto thrust member 74, a spring 76 lifts the valve member 75 off valvemember 68, thereby communicating the chamber 34 with outlet port 78,which connects the chamber 32 with the engine pump 12 inlet.Communication between the chambers 32 and 34 is through a passage 80 ofthe tubular valve member 66 and passage 82 in the central boss 83 of thepiston 35. A spring 84 is located in the central cavity 56 of the pistonfor urging the valve member 66 to the right, as viewed in FIG. I, tocause the valve element 68 to rest against seat 70, cutting offcommunication between the chamber 34 and the inlet port 20.

Under normal conditions of operation, the engine driven pump 12,considered to be the main source of fluid, supplies sufficient fluidunder pressure to successfully operate the power brake boost and thesteering gear 14, independently or concurrently. However, should thepump 12 malfunction or should the pump fail to furnish an adequatesupply of fluid to the vehicle hydraulic system at a time when needed,an extremely dangerous situation would prevail. Either the brake booster10 or the device 14, or both, could be rendered inoperablehydraulically. Of course, both could be operated manually, but this issometimes difficult for a woman. To minimize the likelihood of losingpower for operating the brake booster 10, a second or subsidiaryhydraulic source is made available when the fluid from the first or mainsource reaches a predetermined minimum flow.

The subsidiary hydraulic source is obtained from an electric pump 86having its outlet connected through a line 87 and check valve 88 withinlet port 89 in the housing 16. The inlet port 89 communicates with thebore 18 and recesses 40 and 52, respectively, of the sleeve 36 andpiston 35. A conduit 90 communicates the inlet side of the pump 86 withthe chamber 32 of the boost mechanism 10. Since the pump 86, orsubsidiary source, is to be effectuated or brought into operation onlyif the main source falls to some low flow value, a flow sensitiveswitching device 92 is located in the line 28 to sense such low flow andactuate the electric pump 86. Since the electric pump 86 functions onlyin emergencies as a subsidiary or auxiliary to the engine driven pump 12to furnish fluid only to the brake booster, the pump capacity of pump 86is small compared to pump 12 and is not such that it can supply fluid tothe steering gear too.

With reference to FIG. 2, it will be observed that the housing 16 isprovided with a drilled passage 94, intersecting the working port 26. Aplunger 96, responsive to effectuation of said second source, isslidably received in said passage 94 to interrupt communication betweensaid device and the bore 18. A spring 98 urges the plunger to the right,as viewed in FIG. 2, to permit free flow of fluid from the bore 18 tothe device 14 as long as the first or main hydraulic source ismaintaining the fluid requirements of the system. A passageway 100 inthe housing communicates the back side of a shut-off valve or plunger 96with the outlet of the electric pump 86 through pipe 102. A sphericalplug 104 closes the end of the drilled passage 94. As shown in FIG. I,fluid shunt connection 106 and a check valve 108 provide communicationbetween the working port 26 and the cavity in the bore adjacent recesses40 and 52 to allow for circulation of fluid in an otherwise closed fluidcircuit due to the action of the shutoff valve 96 cutting out device 14.The check valve 108 acts to equalize the pressures between the cavitiesfonned by the recesses 38 and 40 and the bore 18. The electric pump 86is provided with its own internal by-pass device, not shown, from theoutlet to the inlet to permit recirculation of the fluid should thepressure head at the outlet of the pump 86 reach a predetermined highvalue.

MODE OF OPERATION Assuming that the pump 12 is operating properly, i.e.,the main source of fluid is adequate, fluid circulates freely throughthe inlet port 20, recesses 40 and 52, passage 53, the opening betweenvalve seat 72 and valve member 68, passage 55, recess 42, passage 44,recess 38, working port 26, steering gear 14, and back to pump 12.Operation of the brake booster at this time seats the valve member 75 onthe valve member 68, to first cut off the chamber 34 from outlet port78, via the tubular member 66. Continued movement of the members 74 and75 unseats the valve 68 from the seat 70, thus connecting the chamber 34to the main fluid pressure source in communication with the inlet port20. Further movement of the members 74 and 75 seats the valve 68 on seat72. At this moment the chamber 34 is exposed to the full main pressuresource, except that which is by-passed through the axial passages 71 toprovide fluid for operation of the gear 14. This moves the piston 35 tothe left to thereby act on the force transmitting rod 60 to activate abrake master cylinder in a well-known manner. Release of applying forcefrom the thrust member 74, returns the piston means 30 and valve means58 to the present positions, as shown.

In the event that there is an insufficient supply of fluid from the mainsource, at a time when the brake booster is being operated, thisdeficiency will be sensed by the flow sensitive device 92 which actuatesthe electrical pump 86. This effectuates a subsidiary source of fluidwhich is ample for operating the brake booster alone. The pump 86, whichis connected to the inlet port 89 of the booster, communicates withrecesses 40 and 52, passage 53, the opening between valve seat 72 andvalve member 68, passage 55, recess 42, passage 44, recess 38 andworking port 26. These are the same recesses and passages with which themain fluid source communicates. However, the subsidiary source from thepump 86 also acts through conduit 102 and passage on the valve member 96to shut off communication between the working port 26 and the rest ofthe vehicle hydraulic system, including the steering gear 14. This meansthat a much lower capacity pump can be used for the subsidiary sourcesince only the brake booster is controlled by the second source, withthe steering gear out of the hydraulic circuit. When operating under thesecond or subsidiary source of fluid, circulation within the pistonmeans and valve means occurs through the shunt path 106 which connectsthe recesses 38 and 40 of the sleeve 36. Manipulation of the brakebooster is the same irrespective of which of the sources is used.

What is claimed is:

1. In a vehicle hydraulic system:

a hydraulic boost mechanism and a hydraulic device;

said boost mechanism including a housing forming a bore in which pistonmeans is slidably received;

a first hydraulic source in fluid communication with said device viasaid bore;

a second hydraulic source normally ineffective and in fluidcommunication with said bore;

operator-operated valve means for controlling the application of saidfirst and second hydraulic sources to said piston means to cause it toreciprocate in said bore;

means responsive to a predetermined minimum flow through said firstsource for effectuating said second source;

second valve means within said housing responsive to the effectuation ofsaid second source for interrupting communication between said deviceand said bore, to thereby conserve the second source solely foractuation of said boost mechanism.

2. The combination, as recited in claim 1, wherein said hydraulic deviceis a steering gear connected hydraulically in series flow relationshipto said hydraulic boost mechanism.

3. In a vehicle hydraulic system, as defined in claim 1, wherein saidfirst hydraulic source is a pump driven from the engine of the vehicle,and the second hydraulic source is an electric pump.

4. In a vehicle hydraulic system, as defined in claim 1, wherein saidoperator-operated valve means comprises an open-center valve whichpermits free flow of fluid from said engine driven pump through saidboost mechanism from the inlet port to the working port, thence to thesteering gear, and back to the pump.

5. The combination, as defined in claim 4, wherein a fluid shunt isconnected from said working port to said inlet port to by-pass fluidaway from said working port and return it to said inlet port to berecirculated.

6. In a vehicle hydraulic system, as defined in claim 4, characterizedin that said operator-operated valve means is located concentricallywithin said piston means.

7. The invention of claim 1:

conduit means communicating said bore with said device;

second valve means within said conduit means for controlling fluidcommunication therethrough; and

means communicating said second valve means with said second hydraulicsource, said second valve means shifting to a position blocking flow offluid through said conduit means when fluid from said second source iscommunicated to said second valve means.

8. In a hydraulic boost mechanism:

a housing provided with a bore; piston means reciprocable in said boreand dividing said bore into two chambers, located at the respective endsof said piston means;

two inlet ports, two outlet ports and a working port in communicationwith said bore;

one of said inlet ports, one of said outlet ports and said working portare connectible to a main fluid source;

the other of said inlet ports and the other of said outlet ports areconnectible to a subsidiary fluid source;

6 operator-,operated valve means slidably positioned within and openedunder the influence of a spring.

said piston means for controlling fluid flow between said 9. Thehydraulic boost, as defined in claim 8, wherein said ports and saidchambers; valve means includes an open-center valve which permits freemeans responsive to a predetermined minimum fluid flow flow of fluidbetween said one of said inlet ports and said through said working portfor establishing fluid flo at 5 working port during an unappliedcondition of the boost the other of said inlet ports; and mechanism.means in said housing responsive to fluid under pressure at The y r b asdefined claim wherein 88111 the other of said inlet ports forinterrupting fluid flow flow TFSPOHSiVe means prises a flow sensitivedevice f id ki port; operatively connected to an electric pump which isin fluid Said lastmamed means including a Slide valve which is 10pressure communication with the other of said inlet ports.

closed by the fluid pressure at the other of said inlet ports

1. In a vehicle hydraulic system: a hydraulic boost mechanism and ahydraulic device; said boost mechanism including a housing forming abore in which piston means is slidably received; a first hydraulicsource in fluid communication with said device via said bore; a secondhydraulic source normally ineffective and in fluid communication withsaid bore; operator-operated valve means for controlling the applicationof said first and second hydraulic sources to said piston means to causeit to reciprocate in said bore; means responsive to a predeterminedminimum flow through said first source for effectuating said secondsource; second valve means within said housing responsive to theeffectuation of said second source for interrupting communicationbetween said device and said bore, to thereby conserve the second sourcesolely for actuation of said boost mechanism.
 2. The combination, asrecited in claim 1, wherein said hydraulic device is a steering gearconnected hydraulically in series flow relationship to said hydraulicboost mechanism.
 3. In a vehicle hydraulic system, as defined in claim1, wherein said first hydraulic source is a pump driven From the engineof the vehicle, and the second hydraulic source is an electric pump. 4.In a vehicle hydraulic system, as defined in claim 1, wherein saidoperator-operated valve means comprises an open-center valve whichpermits free flow of fluid from said engine driven pump through saidboost mechanism from the inlet port to the working port, thence to thesteering gear, and back to the pump.
 5. The combination, as defined inclaim 4, wherein a fluid shunt is connected from said working port tosaid inlet port to by-pass fluid away from said working port and returnit to said inlet port to be recirculated.
 6. In a vehicle hydraulicsystem, as defined in claim 4, characterized in that saidoperator-operated valve means is located concentrically within saidpiston means.
 7. The invention of claim 1: conduit means communicatingsaid bore with said device; second valve means within said conduit meansfor controlling fluid communication therethrough; and meanscommunicating said second valve means with said second hydraulic source,said second valve means shifting to a position blocking flow of fluidthrough said conduit means when fluid from said second source iscommunicated to said second valve means.
 8. In a hydraulic boostmechanism: a housing provided with a bore; piston means reciprocable insaid bore and dividing said bore into two chambers, located at therespective ends of said piston means; two inlet ports, two outlet portsand a working port in communication with said bore; one of said inletports, one of said outlet ports and said working port are connectible toa main fluid source; the other of said inlet ports and the other of saidoutlet ports are connectible to a subsidiary fluid source;operator-operated valve means slidably positioned within said pistonmeans for controlling fluid flow between said ports and said chambers;means responsive to a predetermined minimum fluid flow through saidworking port for establishing fluid flow at the other of said inletports; and means in said housing responsive to fluid under pressure atthe other of said inlet ports for interrupting fluid flow from saidworking port; said last-named means including a slide valve which isclosed by the fluid pressure at the other of said inlet ports and openedunder the influence of a spring.
 9. The hydraulic boost, as defined inclaim 8, wherein said valve means includes an open-center valve whichpermits free flow of fluid between said one of said inlet ports and saidworking port during an unapplied condition of the boost mechanism. 10.The hydraulic boost, as defined in claim 8, wherein said flow responsivemeans comprises a flow sensitive device operatively connected to anelectric pump which is in fluid pressure communication with the other ofsaid inlet ports.